Earth Science Enterprise Science and Technology for Society
By Earnest D. Paylor, II, Ph.D., Jack A. Kaye, Ph.D., Anngienetta R. Johnson, and Nancy
G. Maynard, Ph.D.

The Earth is a dynamic system of land, oceanic, atmospheric, and biologic processes. These processes are interconnected by an intricate and fragile web that helps modulate such things as weather, droughts, and floods and can ultimately have profound impacts on global food production, natural resource management, commerce, and the global economy. The recently experienced 1997-98 El Ni–o cycle illustrates this complex interaction, beginning when the normal state of the Pacific ocean was perturbed by a weakening of the westerly trade winds; a state that is necessary to maintain a ÒpoolÓ of warm water within the western tropical Pacific. The weakening of trade winds allowed warm water to flow eastward along the Equator to coastal Peru. The eastward-spreading water brought with it the associated tropical rainfall. As the warm pool reached the coast of Peru, it spread to the north and south progressively, cutting off the nutrient-rich upwelling along the Peruvian coast, causing a collapse of the fishery, and impacting the seabird population. As the heat from the warm pool escaped into the atmosphere, it impacted global atmospheric circulation, including the global jet streams. This perturbed atmospheric state brought unusual weather around the world, where normally wet regions such as Indonesia and northern Australia experienced drought and wildfires, and normally dry regions such as southern California experienced floods and mudslides. These changes, in turn, had a significant impact on plant, animal, and human life. The disruption to society was profound: the last cycle was associated with an estimated $8 billion in economic losses.
    The complex El Ni–o phenomena illustrate the need for the multidisciplinary, systems approach to its study. NASAÕs Earth Science Enterprise endeavors are to understand such complex phenomena related to the total Earth system and the effects that natural and human-induced changes have on the global environment. From the unique vantage point of space, ESE and its partners are beginning to understand these dynamic and interacting processes. The fundamental knowledge gained in this is also being used for practical societal needsÑsuch as more accurate weather and climate forecasting, precision farming and forestry, natural resource management, urban and regional planning, disaster management, human health and safety planning, and more.
    ESE has implemented a complex program including science and applications research, observational systems and technology development, and information system management, in cooperation with domestic and international partners. In short, NASA is poised to bring together the powerful combination of science, space-based remote sensing, and information system technologies to enable policy and decision makers at all levels of the government, public, and private sector practitioners to establish sound, knowledge-based environmental decisions in the 21st Century.

Science of the Earth System
To study the Earth, NASA is taking full advantage of a strong and complex program of fundamental research in Earth system science. Satellite and airborne remote sensing observations coupled with ground-based measurements and powerful computers are used to achieve a basic understanding of the EarthÕs large-scale processes such as changes in the atmosphere or forests, and to mimic, or model, the behavior of the Earth system at the regional-to-global scale. These large-scale investigations continue as a critical part of the ESE scientific endeavor because they form the context within which to gain understanding of regional-to-local scale concerns. As the behavior of the EarthÕs past climate is successfully modeled, confidence is gained that future long- and short-term trends can someday be predicted. The information resulting from these efforts is necessary to address local-scale concerns such as suburban land use planning, natural resource management, or disaster mitigation. Both the growth in scientific understanding and the needs of economic and policy decision-makers are leading ESE to formulate more focused questions such as:

Is climate changing in ways we can understand and predict?
ESE will attempt to uncover the basic mechanics of climate, and then distinguish natural from human-induced impacts on the climate system leading to more accurate predictive models of ocean-atmosphere interactions, cloud formation, radiative balance, and chemical transport from land to atmosphere. This predictive knowledge can then be translated to support decisions based on improved understanding of short-term weather and seasonal climate variations. A good example is that based on satellite observations, scientists were able to predict the 1997-98 El Nino approximately 6 months beforehand and monitor its progression. This gave decision-makers time to plan mitigation strategies, including planting alternate crop types and modifying harvest schedules, implementing flood control activities, and better preparing for El NinoÕs impacts in general.

Can we understand and predict how terrestrial and marine ecosystems are changing?
ESE will attempt to distinguish natural from human-induced changes in ecosystem characteristics. Uncertainties in understanding of carbon and nitrogen cycles are being addressed. More reliable knowledge is needed of the ability of ecosystems to recover from disturbances, human-induced or natural, and of implications regarding the long-term sustainability of the planetÕs biological productivity. This information is directly applicable, for example, to natural resource management, and can support decisions makers and practitioners in agriculture, food production, and fishery industries.

How is the chemical composition of the atmosphere changing?
NASA has made great strides in understanding the concentrations and distributions of ozone and ozone-depleting chemicals in the stratosphere. Detailed studies of the ozone layer as it recovers, expected as the result of the banning of chloroflorocarbons (CFCs), will be carried out. A better understanding of the chemistry in the lower atmosphere, where humans live, is needed to determine the consequences of human-produced ozone and other pollutants, and to better understand the combined effects of global climate change and global pollution.

Can we improve our understanding of the processes and dynamics of the EarthÕs surface and interior, and use this knowledge to prepare for and respond to natural hazards such as volcanoes and earthquakes?
NASA seeks to understand the dynamics of the solid Earth and its interaction with the atmosphere, oceans, and biosphere. Fundamental scientific questions about the rates and magnitudes, and the spatial and temporal variability of these dynamics remain unanswered. Such information also provides critical knowledge to improve assessments of the vulnerability to natural hazards, and to predict and mitigate the consequences of natural disasters.

Observations and Measurement Strategies
Phase I of the ESE program has been comprised of focused, free-flying satellites, space shuttle missions, and various airborne and ground-based studies. Phase I has provided global measurements of major Earth system components. Their purpose was to improve our knowledge of basic processes prior to the Earth Observing System (EOS) era. These include: 1) the currently operating Upper Atmosphere Research Satellite (UARS), which confirmed the anthropogenic origin of ozone-depleting substances; 2) TOPEX/Poseidon, which is detecting variations in sea level world-wide; 3) the NASA Scatterometer (NSCAT), which detected ocean surface wind vectors from JapanÕs ADEOS satellite; 4) the SeaWiFS mission, which is providing ocean color information useful to understanding biological productivity in the oceans; and 5) the Tropical Rainfall Measuring Mission (TRMM), also conducted jointly with Japan, which for the first time is providing an accurate assessment of the structure of storm systems, rainfall, and associated energy release over the oceans in the low latitudes.
    Phase II of ESE begins this year with the launch of Landsat 7 and the EOS satellites. EOS is the first observing system to offer integrated measurements of the EarthÕs processes and will generate a long-term environmental database focusing on climate change. EOS will usher in an unprecedented observational capability for understanding the planet. EOS, the largest element of NASAÕs ESE observational program, is a program of multiple spacecraft designed to provide measurements of key, multi-disciplinary parameters needed to understand global climate change. The first spacecraftÑTerra (formerly called EOS AM-1) and Landsat 7Ñare scheduled for launch this year. The instruments aboard Terra will enable scientific studies of the physical and radiative properties of clouds; air-land and air-sea exchanges of energy, carbon, and water cycles; measurements of trace atmospheric gases; and other land processes. Landsat 7 will make important land-use and land processes measurements, complementing and improving upon those made by previous Landsat spacecraft in building the largest database of medium resolution land surface images of EarthÕs continents since 1972. The EOS PM-1 and Chemistry-1 missions will help achieve an understanding of short-term weather and atmospheric chemistry. The EOS program also includes several small satellites such as the joint venture with France known as Jason-1 (a follow-on to the highly successful TOPEX/Poseidon mission), QuikScat, ICESat, SoRCE, and ACRIM.
     Phase III of ESE represents missions that are complementary in nature to EOS and address unique, specific, and highly focused mission requirements in Earth science research, called Earth probes. The program was designed to have the flexibility to take advantage of unique opportunities presented by domestic/international cooperative efforts and/or technical innovation. It complements EOS by providing the ability to investigate specific Earth processes that require special orbits or have unique observation requirements. Currently approved Earth probes include: the Shuttle Radar Topography Mission (planned for launch in September 1999), which will provide the first global (within about 60 degrees North and South latitude) moderate-resolution digital topographic characterization of the EarthÕs land surface; the Stratospheric Aerosol Gas Experiment-Russian/Meteor; and the Earth System Science Pathfinder missions (Vegetation Canopy Lidar, the Gravity Recovery and Climate Experiment, and PICASSO-CENA).
    Embracing the NASA Òfaster, better, cheaperÓ philosophy and pursuing advanced technological developments, ESE intends to drastically shrink the size, cost, and development time for missions in the next decade while maintaining capabilities and performance of these systems. Such missions will be more sharply focused on addressing specific science or application questions, rather than conducting broad surveys. An integrated technology program is paving the way for a Òfaster, better, cheaperÓ mission set. The Instrument Incubator Project, for example, supports the development of new instruments and measurement techniques from concept to laboratory development and ground or air validation. The New Millennium Program focuses on identifying and demonstrating advanced technologies or engineering capabilities in orbit that reduce cost or improve performance of spacecraft instruments for future. Upcoming new millennium missions include the Earth Observing mission (EO-1), which will carry an Advanced Land Imager in December 1999, and the Space-Readiness Coherent Lidar Experiment aboard the space shuttle in January 2001.

The Applications Imperative
As stated previously, ESE has recognized that its knowledge and data have significant practical value to society and, therefore, is fostering increased access to, and use of, the information to make better, more informed decisions on a daily basisÑdecisions regarding important issues such as those related to weather and climate forecasting, flood monitoring and mitigation, agriculture productivity, natural resource management, urban and regional planning, drought impact assessment, and transportation planning. To this end, ESE formulated and implemented a new program aimed at application research and commercial developments, including communication of ESE data and science to the non-science communities.
    The content of this new initiative is defined based upon application issues, similar in concept to the high-level science issues and questions that drive the scientific research in ESE. The major difference is that the application issues are defined by public and private sector markets and necessities, and not scientific curiosity. The current application issues include food and fiber, natural resources, disaster management, environmental quality, urban and infrastructure, and human health and safety.

Communication of Information and Knowledge
The EOS Data Information System (EOSDIS) is the backbone of ESEÕs ability to convert raw remote sensing data to information and communicate that to science and application users. In addition to serving thousands of current users, EOSDIS will operate the EOS spacecraft, acquire, and distribute the basic data gathered by the instruments. It provides the basis for both the government and its commercial and academic partners to generate the higher-level data products that will make the measurements more easily understandable and usable by researchers, educators, policy makers, and the public.
    EOSDIS will process and archive nearly all ESE data, making it one of the largest civilian information systems ever conceived. The enormous variety and utility of these data, and consequently the wide variety of potential users, make creation and distribution of final data products a challenge. ESE is also establishing a ÒfederationÓ through Earth Science Information Partners (ESIPs) who will participate in producing and distributing selected data products to different groups of users. If EOSDISÕ federation is successful, eventually all higher-order data products will be produced by competitively selected ESIPs. ESE will continue to utilize new and creative mechanisms such as regional applications centers and extension networks to communicate its data and information to the science and applications communities, as well as the general public (see article by Martha Maiden and Timothy Gubbels in this issue).

Partnerships
In a program as diverse and complex as ESE, it is virtually impossible to implement without cooperation and collaboration from external sources. ESE employs a multifaceted approach to making and using Earth science information by significant cooperation and partnerships with other Federal agencies, the commercial sector, and the international community. EOS, for example, is already integrated with climate-related research and capabilities conducted by seventeen other Federal agencies through the U.S. Global Change Research Program (USGCRP). ESE will continue increasing its partnerships with Federal agencies as it continues expanding, particularly though its application efforts. Recognizing the continued emergence and expansion of many commercial remote sensing capabilities, ESE is also attempting to stimulate the development of this sector, both as a provider and a user of ESE data. Developing commercial capabilities can enhance efficiency in the ESE science mission and promote the long-term stability required by science research and commerce (see article by Bruce Davis in this issue).
    In the international arena, ESE is leveraging its investments through partnerships with other nations. Foreign governments are providing instruments to fly on ESE satellites, and the U.S. is providing instruments for other nationsÕ satellites. ESE also negotiates for access to data from non-U.S. missions. This not only stretches the dollars invested in ESE by American taxpayers, but also builds world-wide confidence in scientific results and environmental assessments. The outcome and payoff of this international involvement extends to the development of a framework for nations to commit to fulfilling requirements of an international global observing strategy. The total amount for international partner investments is approximately equal to U.S. investment. In addition to sharing of costs, international partners contribute through their professional and intellectual expertise, through their early involvement in the program, endorsing and embracing scientific outcome of these collaborative efforts, paving the way for international policy decisions.

Summary
NASA, together with its partners in the U.S. government and around the world, have responded to the challenge of Earth system science by developing complementary and interconnected observations, data/information systems, and analysis capabilities designed to provide the most cost-effective means of conducting the science and conveying that information to societal uses through the ESE program. The resulting science and applications will provide U.S. leadership in the development of an international consensus on the state of the Earth today and in the future. This approach will yield long-term predictions of the state of the Earth system, as well as provide practical information that will benefit practitioners, policy makers, educational institutions, the business community, and the public at large. Just as weather and communications satellites changed the way we view and perceive those fields, the elements of ESE will change the way we perceive the EarthÕs environment and climate in the 21st Century.

About the Author:
Dr. Earnest D. Paylor, II, Dr. Jack A. Kaye, Anngienetta R. Johnson, and Dr. Nancy G. Maynard work in the Office of Earth Science at NASA Headquarters in Washington D.C.

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